Effective schizophrenia recognition using discriminative eye movement features and model-metric based features

Spatial and Temporal Abnormalities of Spontaneous Fixational Saccades and Their Correlates With Positive and Cognitive Symptoms in Schizophrenia

BACKGROUND AND HYPOTHESIS

Visual fixation is a dynamic process, with the spontaneous occurrence of microsaccades and macrosaccades. These fixational saccades are sensitive to the structural and functional alterations of the cortical-subcortical-cerebellar circuit. Given that dysfunctional cortical-subcortical-cerebellar circuit contributes to cognitive and behavioral impairments in schizophrenia, we hypothesized that patients with schizophrenia would exhibit abnormal fixational saccades and these abnormalities would be associated with the clinical manifestations.

STUDY DESIGN

Saccades were recorded from 140 drug-naïve patients with first-episode schizophrenia and 160 age-matched healthy controls during ten separate trials of 6-second steady fixations. Positive and negative symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). Cognition was assessed using the Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus Cognitive Battery (MCCB).

STUDY RESULTS

Patients with schizophrenia exhibited fixational saccades more vertically than controls, which was reflected in more vertical saccades with angles around 90° and a greater vertical shift of horizontal saccades with angles around 0° in patients. The fixational saccades, especially horizontal saccades, showed longer durations, faster peak velocities, and larger amplitudes in patients. Furthermore, the greater vertical shift of horizontal saccades was associated with higher PANSS total and positive symptom scores in patients, and the longer duration of horizontal saccades was associated with lower MCCB neurocognitive composite, attention/vigilance, and speed of processing scores. Finally, based solely on these fixational eye movements, a K-nearest neighbors model classified patients with an accuracy of 85%. Conclusions: Our results reveal spatial and temporal abnormalities of fixational saccades and suggest fixational saccades as a promising biomarker for cognitive and positive symptoms and for diagnosis of schizophrenia.

Air traffic control forgetting prediction based on eye movement information and hybrid neural network

Control forgetting accounts for most of the current unsafe incidents. In the research field of radar surveillance control, how to avoid control forgetting to ensure the safety of flights is becoming a hot issue which attracts more and more attention. Meanwhile, aviation safety is substantially influenced by the way of eye movement. The exact relation of control forgetting with eye movement, however, still remains puzzling. Motivated by this, a control forgetting prediction method is proposed based on the combination of Convolutional Neural Networks and Long-Short Term Memory (CNN-LSTM). In this model, the eye movement characteristics are classified in terms of whether they are time-related, and then regulatory forgetting can be predicted by virtue of CNN-LSTM. The effectiveness of the method is verified by carrying out simulation experiments of eye movement during flight control. Results show that the prediction accuracy of this method is up to 79.2%, which is substantially higher than that of Binary Logistic Regression, CNN and LSTM (71.3%, 74.6%, and 75.1% respectively). This work tries to explore an innovative way to associate control forgetting with eye movement, so as to guarantee the safety of civil aviation.

The impact of COVID-19 pandemic on individuals at clinical high-risk for psychosis: Evidence from eye-tracking measures

Emerging evidence suggested that people with severe mental disorders were more vulnerable to the negative effects of the COVID-19 pandemic. However, few researches investigated the influence of global pandemics on people at clinical high risk (CHR) for psychosis. This study aimed to investigate the impact of the COVID-19 pandemic on clinical symptoms, psychological distress, and eye-tracking characteristics in CHR individuals and healthy participants. Forty-nine CHR individuals and 50 healthy controls (HC) were assessed by PTSD Checklist for DSM-5 (PCL-5), Perceived Stress Scale, 10-item version (PSS-10), and Coronavirus Impact Scale (CIS). Eye movement performances were measured by the tests of fixation stability, free-viewing, and anti-saccade. According to the mean score of CIS, participants were stratified into high-impact (n = 35) and low-impact (n = 64) subgroups. Compared with the HC group, CHR participants reported significantly higher levels of post-traumatic symptoms caused by the COVID-19 pandemic and showed abnormalities in most of the eye movement indexes. Among the altered indexes, the saccade amplitude of fixation stability test (far distractor), the scan path length of free-viewing test, and the accuracy of anti-saccade test were negatively affected by the severity of impact level in the CHR group. Moreover, the altered eye movement indexes were significantly associated with the total scores of CIS, PCL-5, and subscales of the Scale of Prodromal Syndromes (SOPS) among CHR individuals. Overall, our findings suggested the negative impact of the COVID-19 pandemic on the eye movement characteristics of CHR individuals. The present study provides valuable information on physiological distress related to the COVID-19 pandemic and sensitive neuropsychological biomarkers that interacted with social and environment stress in the CHR population.

Eye movement indices as predictors of conversion to psychosis in individuals at clinical high risk

Eye movement abnormalities have been established as an "endophenotype" of schizophrenia. However, less is known about the possibility of these abnormalities as biomarkers for psychosis conversion among clinical high risk (CHR) populations. In the present study, 108 CHR individuals and 70 healthy controls (HC) underwent clinical assessments and eye-tracking tests, comprising fixation stability and free-viewing tasks. According to three-year follow-up outcomes, CHR participants were further stratified into CHR-converter (CHR-C; n = 21) and CHR-nonconverter (CHR-NC; n = 87) subgroups. Prediction models were constructed using Cox regression and logistic regression. The CHR-C group showed more saccades of the fixation stability test (no distractor) and a reduced saccade amplitude of the free-viewing test than HC. Moreover, the CHR-NC group exhibited excessive saccades and an increased saccade amplitude of the fixation stability test (no distractor; with distractor) compared with HC. Furthermore, two indices could effectively discriminate CHR-C from CHR-NC with an area under the receiver-operating characteristic (ROC) curve of 0.80, including the saccade number of the fixation stability test (no distractor) and the saccade amplitude of the free-viewing test. Combined with negative symptom scores of the Scale of Prodromal Symptoms, the area was 0.81. These findings support that eye movement alterations might emerge before the onset of clinically overt psychosis and could assist in predicting psychosis transition among CHR populations.

Effective differentiation between depressed patients and controls using discriminative eye movement features

BACKGROUND

Depression is a common debilitating mental disorder caused by various factors. Identifying and diagnosing depression are challenging because the clinical evaluation of depression is mainly subjective, lacking objective and quantitative indicators. The present study investigated the value and significance of eye movement measurements in distinguishing depressed patients from controls.

METHODS

Ninety-five depressed patients and sixty-nine healthy controls performed three eye movement tests, including fixation stability, free-viewing, and anti-saccade tests, and eleven eye movement indexes were obtained from these tests. The independent t-test was adopted for group comparisons, and multiple logistic regression analysis was employed to identify diagnostic biomarkers. Support vector machine (SVM), quadratic discriminant analysis (QDA), and Bayesian (BYS) algorithms were applied to build the classification models.

RESULTS

Depressed patients exhibited eye movement anomalies, characterized by increased saccade amplitude in the fixation stability test; diminished saccade velocity in the anti-saccade test; and reduced saccade amplitude, shorter scan path length, lower saccade velocity, decreased dynamic range of pupil size, and lower pupil size ratio in the free-viewing test. Four features mentioned above entered the logistic regression equation. The classification accuracies of SVM, QDA, and BYS models reached 86.0%, 81.1%, and 83.5%, respectively.

CONCLUSIONS

Depressed patients exhibited abnormalities across multiple tests of eye movements, assisting in differentiating depressed patients from healthy controls in a cost-effective and non-invasive manner.